This invention relates to novel compositions of matter, to novel methods for producing those, and to novel chemical intermediates useful in those processes. Particularly, this invention relates to a process for preparing certain novel analogs of prostaglandin F.sub.1.sub..alpha. in which the C-5 methylene (--CH.sub.2) in the prostanoic acid structure is replaced by oxygen (--O--), represented by the formula: ##STR1## wherein the terms O, R.sub.2, R.sub.3, R.sub.4, R.sub.4, R.sub.25, and R.sub.26 are defined herein.
The essential material for this application, including the background of the invention, the disclosure of the invention, and the description of the preferred embodiments, including Preparations and Examples, is incorporated by reference from U.S. Pat. No. 3,931,279 columns 1-67 and 73-86, inclusive, under the provisions of M.P.E.P. 608.01(p).